The replace blueprint interface currently uses a select. This is difficult to navigate when many blueprints are present across many folders.
It would be a better user experience if the blueprint replace interface used the file explorer to allow folder navigation.
I have this issue too. Additionally, a searchbar would be nice to quickly search for the name of the blueprint you want to replace.

Current workaround is to copy the blueprint to your clipboard (enabled by default) and use right-click -> “Replace” in your blueprint library.