I have been interested by Scottish culture - to varying degrees, sometimes very intensely - for forty years, when my family moved there. I have myself lived in Scotland 'solo' for more than three years, and family connections continue.
One thing has become clear is that Scottish Nationalism has been thoroughly corrupted over the past few decades - in a nutshell, it has moved from being (overall) based-on Patriotism, to being based on Resentment - specifically anti-English animus.
In other words it has gone from being rooted-in Love of one's own-country, to hatred of another-Country
This has often been the fate of Nationalism whenever it takes a political form - because it is much easier to encourage and sustain resentment than love.
Almost all nationalisms have been defined-against - in the sense that there is a threat to the culture that is resisted. Almost every nation has an excluded-other. For Germany and for England this was France (which annoyed Scotland and Wales, because they defined themselves against England) - for France it was England (which annoyed the Germans, who felt slighted).
It is interesting that the most notorious nationalism of recent years - Germany 1933-45 - was a fake nationalism, directed against a newly-invented rival-enemy distinctive only to the Party leadership. This suggests that the mass-popular roots of support for the National Socialist Workers' Party was quite probably genuine patriotism, i.e. love of country; as against the anti-patriotism and cultural destruction advocated by the rival forces of International Socialism/ Communism.
Scottish 'nationalism' (ie. loving patriotism) emerged after the Union of Parliaments with England and Wales, in 1707; and was most exemplified by people like Sir Walter Scott - who were strongly in favour of this Union. In other worlds, cultural patriotism was distinct from political Unionism. There followed a great era of Scottish creativity and intellectual attainment - during which Scotland was an international leader in philosophy, medicine, technology, science, universities; as well as literature (the likes of Byron, Burns, Scott, Stevenson). The Scots became cultural arbiters, and Edinburgh was known as the Athens of the North.
Modern political nationalism emerged, I think, due to the centralising and controlling tendency of the modern State from the late 1800s; which put ever increasing pressure on the social forms of distinctness.
For example, in Scotland, the Union into Britain exempted Scots Law, Education and the Church - but the modern State was continually eroding the autonomy of these institutions - and imposing a uniform centralised government.
So, the desire for political autonomy was understandable. But, because it was political, it was almost-certain to be operationalised towards maximising the benefits of politicans.
There was a referendum about increased Scottish devolution in 1979, which resulted in a majority in favour of devolution - but this was claimed (by the prior definition of margin required) to be too small a proportion of the population to lead to change.
Thus, the result was genuinely ambiguous - but instead of being clarified it was ignored - thereby contributing to a building anti-English resentment as the 'local' Scottish elites saw the opportunity for a power/ wealth grab, as putative leaders of a pseudo-independent Scotland: under the slogan of Independence In Europe. The idea was to separate from England, but remain a part of the European Union.
(At that time, the smaller-economy nations who joined the EU - e.g. Ireland, or Spain - were being bribed with pretty lavish public-works subsidies - mostly harvested by France from Germany, the UK and the Netherlands. Later bribery to lure nations into the Union became restricted to the pockets of decision-making elites.)
But I say this was 'pseudo'-independence because no Scottish patriot (no-one who loved Scotland - its people, its culture) would wish to stay within the European Union. Leaving Britain but remaining in the EU would make very little difference when most of the national laws and cultural changes derive from the EU.
More decisively, the EU is strategically-dedicated to obliterating national cultures and creating a single culture; a single 'zone' to be homogenised and colonised and overrun by massive and sustained migration and immigration.
The fact that Scottish 'independence' is envisaged within the EU reveals the dishonesty of any pretence of patriotism; and explains the escalation of explicit anti-English sentiment in the Scottish Parliament, mass media and social institutions.
For me, a threshold arrived just over a decade ago when the Scottish government abolished tuition fees in Scottish Universities. The plan was to offer free tuition to all European Union nations except for England (who, of course, supply most of the tax incomes to pay for this subsidy). In practice, Scotland was legally-compelled also to charge tuition fees to students from Wales and Northern Ireland - but officials apologised for this, because it was only England who was being targeted.
This, then, is a measure of the corruption of Scottish nationalism into a crude combination of anti-English resentment and servile rent-seeking: the cause of its basis in spiteful Schadenfreude rather than love; and the strategic desire for a life of subsidised hedonism rather than creative endeavour.