Pasting items in large projects becomes unusably slow

In projects with about 3,000 items or more, pasting any number of items in the arrange view will be executed with a frustrating delay. Check this demo project, which was used to demonstrate another (similar, sorta, project size-related) problem: (with media: ) Try copying the little MIDI item at the top, and pasting it. Delete groups of tracks beneath to see how REAPER responds with different numbers of items. ~1,500 items: delay barely tangible, not a problem. ~3,000 items: tangible delay, definitely problematic. ~12,000 items: unusable delay, depending on the speed of pasting. At and above ~3,000 items, pasting a single item once is delayed. The size of the item doesn't seem to matter. But try pasting the item repeatedly, e.g. Ctrl-C, Ctrl-V Ctrl-V Ctrl-V Ctrl-V (etc.) At ~3,000 items: REAPER just about keeps up. At ~12,000 items, the paste commands get horribly queued up, and you can watch REAPER take a long time to carry them out. It would be great to see this kind of issue sorted out. Let me know what you think! Cheers.

Now here: Check it. Thanks.

containers, with ghost copy.. mmmm.. :) maybe on one fine day confirmed, btw.