Thanks for the positive feedback and for your question. There are a couple of ways to make your task easier.
First, you can assign terms and ALT Text values as you upload your images. Go to the Media/Add New (Upload New Media) screen and click on the “Open Bulk Edit area” button before you drag & drop your images onto the screen. With the Bulk Edit area you can make all the changes you need, and they will be applied to the images as they are placed in the Media library.
Second, for the images already in the Media Library, you can change the number of entries displayed on each page of the Media/Assistant submenu table. Click on the “Screen Options” button at the top-right of the screen, then change the number of “Entries per page”. If you set it to 50 or 100 you can process 300 images in 6 or 3 passes.
If you set the per page number to a high value you may want to disable “where-used” reporting to improve performance. Go to the Settings/Media Library Assistant General tab and scroll down to the “Where-used database access tuning” section. Make sure all four entries are set to “Disabled”. That will make the Media/Assistant submenu table load faster.
I hope the above suggestions give you some help with your editing tasks. I am marking this topic resolved, but please update it if you have any problems or further questions regarding the Bulk Edit options in MLA. Thanks for your interest in the plugin.
