As per this entry Share multiple files from gallery
it seems there’s no way to share multiple entries from gallery at once. instead one need to open every single photo one by one, then click share, pickup share option (say BT), then pickup device. When you need to do this like 20 times it’s becoming a big problem.
Jolla gallery already has multiselect functionality in the gallery but it only allows to delete multiple photos at once, please expand it so sharing multiple files will be also possible. It should also work for mms in that case multiple mms should be sent maybe with confirmation in this case.