Tailoring CB Gallery

There is no functionality for that. That's something you would have to completely implement yourself. You'd have to use CB Auto Actions to act on the following triggers.

PM Form:
pm_onAfterDisplayMessageEdit
pm_onAfterDisplayMessageReply

PM Display:
pm_onAfterDisplayMessage

PM Save:
pm_onAfterCreateMessage

This is not likely to be a simple task. The easiest thing for your users to do is like any other social media site. Simply copy and paste the URL. Even for photos they can right click, copy image url, and paste it. In a future release it maybe possible to insert media from their profile gallery, but I've no idea when I will get to that.

Hi Kyle.
Here is how I customized the new message form without breaking anything at first glance:

• Copy and rename this folder: components/com_comprofiler/plugin/user/plug_pms_mypmspro/templates/default/
• Select the corresponding new folder in Admin > Community Builder > Private Messages > Configuration > Parameters > General > Template
• Edit this file in the new folder: message_edit.php

By editing message_edit.php, I was able to add a "Select the album to send" checkbox field that uses javascript to add links to the selected albums at the end of the message when the submit button is clicked. I can share my message_edit.php if it might be of interest to you.
For now, this solution is fine because it works.
But I need to improve it for a more user-friendly experience: how can I force the PM file upload box to automatically add the uploaded file to the sender's latest album?
Thanks.

You can't without re-implementing the CB Gallery integration using CB Auto Actions. CB Gallery integration to PMS is hardcoded into CB Gallery. You're effectively needing something wildly different than what is available so you've to implement your own solution. The CB Gallery implementation is as follows if you want to try and replicate it in CB Auto Actions and change it to fit your needs.

Triggers:
Implementation:
/components/com_comprofiler/plugin/user/plug_cbgallery/library/Trigger/PMSTrigger.php

I do not recommend just making changes to the file above as you will lose those changes when you update CB Gallery.

Ok thanks now that this is clear, could you give an approximate possible release date for this PMS Media Gallery integration?

CB Gallery is already integrated with the PMS. I'm not sure what integration you're waiting for? You mean the WYSIWYG editor button for inserting profile gallery media?

This integration:

In a future release it maybe possible to insert media from their profile gallery, but I've no idea when I will get to that.