Scratch

The easiest way to do that is to export the sprite that holds the scripts (right-click on the sprite > export this sprite) and import it into another project. If this presents problems, you can always make a "dummy sprite" that you can transfer certain scripts to, then export that. Be warned: if an imported sprite's scripts contain references to variables that don't exist in the new project, the variables will be created, whether they are public ("for all sprites") or private ("for this sprite only"). Worse yet, both projects could have a variable with the same name (maybe "count" or "score") that would be changed unexpectedly when the imported scripts are run. Import with caution, and save a backup; it's ruined projects of mine in the past.