If a widget blueprint contain hundreds of another widget blueprint instance, the compiling will very very slow:
In my case there are 200+ instances in the main widget blueprint, the sub widget blueprint only have a button widget in it, 50 minutes passed still Not responding:
I’ve checked in a fix for your use-case, it was forcing the details panel to rebuild for every widget replaced in memory. The compile times should be down around 10 seconds now for 4.5 for that many widgets. Hopefully there will be another preview build before final release you can try out.
I started working on some improvements to the blueprint compiler instance replacement code that will help in 4.6 assuming it’s not riddled with bugs. I was able to get it down to about 1 second for that same case.