Since these are live cases, he could be held in contempt of court, for which the penalties can be rather serious, or he could compromise the chances of a guilty verdict standing.
In any case, he can demand all he likes, he can't buy the Scottish legal system and it's proudly impervious to political pressure.
To my knowledge, three people have been arrested and questioned (in Scotland, police have to arrest you in order to formally interrogate you under caution) in relation to the damage, and so far only one man has been charged. Any cases arising will be passed to the procurator fiscal's office to assess the evidence and decide whether to proceed to trial. The chances of the accused's actions being judged as "terrorism" are laughably small.
Jury trial in criminal cases is reserved for serious offences, which is unlikely to include crime against property, and there's no discretion for the accused to demand a jury for lesser offences (such as the allegations in this case, which would usually be classed as malicious mischief - known as criminal damage in the English legal system - a step up from the lesser Scottish crime of vandalism), which will be tried under summary procedures in sheriff court.
If Trump decided to go for civil litigation, then a 12-person jury would be involved (in criminal cases, it would be 15). The chances of finding enough jury members in Scotland who could swear themselves unbiased where Trump's concerned are slim. In any case, if he did sue, there'd likely be very significant crowdfunding for those he'd be suing, and a media free-for-all that might not do his Scottish clubs any good.
Scottish courts in jury trials have sometimes taken lenient views on what are seen as crimes of conscience, such as the ones alleged here, even refusing to convict.
(IANAL, BTW, but I have been on the wrong end of court cases for political actions in the distant past.)
ETA: The man charged has now appeared in court today: https://news.sky.com/story/man-appears-in-court-charged-with-malicious-mischief-over-damage-to-trump-turnberry-golf-resort-in-scotland-13339366
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