I have attempted to reproduce this issue internally and am able to import All for 100 Static Meshes with only hitting the Import All button once. I tried also adding in Morph Targets and Skeletal Meshes to make more than 100 files and only when the Import hit a different file type did I get another pop up. Can you provide anymore information as to the type of project (have you tested it in a Blank Project) and what type of assets you are importing.
All I’ve done is literally export a few meshes from 3Ds as FBX to the content folder and let Auto Directory in UE4 auto import the files. On the first mesh turn off generate lightmaps (I want to use my own) and hit import all, It then requires me to do it on a per asset basis.
this is still an issue and has never been fixed - i have never been able to import all EVER - I have 23+ projects on 3 different computers with hundreds of models and jsut now for some reason my proect wouldnt open - I had to move some stuff out of directories then move back to get open - when it opened it had to re-import a hundred plus models and - absolutely the import all does not work- I never change anything just import select files - import all - never never never has it ever worked for the past 2 years
For anyone finding this in the future. This bug does not appear when you drag-and-drop into the editor directly.
It does appear when you drop files into the File Explorer, then press Unreal Engine import notification notification.