By "update in place" I meant overwriting original files with the optimized ones. Right now, if you select the same folder for both input and output, KinBo will save optimized files with " (1)" suffix, so to actually replace original files with the optimized ones, you have to export them to some other folder and then replace the original ones via file manager.
And a couple more pieces of feedback:
1. By default, on Boox devices, text on some buttons is unreadable, although it can be fixed via eink tweaks:
https://imgur.com/a/AfTlOvh
2. It would be nice to have an explanation of what some of the options do (e.g., Manga mode).