I’ve opened a Dorico 2 score I was working on in Dorico 3, and have tried to delete an empty player. Fifteen minutes, I’m still waiting… (Computer is https://www.scan.co.uk/3xs/configurator/overclocked-custom-gaming-pc-uk-performancegtkz170 - what do I actually need to make Dorico 3 usable?)
It’s consistently taking about half an hour to add or remove a player. This is not workable.
How many players, flows, bars?
As a workround, try viewing a part (preferably as small as possible) in Galley view, then close and re-open the project, then try editing your players.
That way, Dorico won’t be trying up update the layout of the entire score every time you add a new staff, which is presumably what is taking for ever (though half an hour isn’t reasonable, of course).
Also, switching condensing off saves a lot of unnecessary calculations laying out the score, until you done all the changes to players etc.
Please provide the project you’re working on, and the diagnostic report created by choosing Help > Create Diagnostic Report, so that we can investigate what might be going on.