Problem:
The user would like to use different view's items count per screen. For example, display 9 posts in Desktop and only 3 posts in mobile.
Solution:
Currently, there is no option or setting to change the number of posts per view depending on the screen/device. You can only do it using two views. Put each one inside a container block, and make them show or hide depending the screen.
There is also a hook you can use to programmatically change the settings of a view. The wpv_view_settings hook. Check the example code on it.
Problem:
The user would like to add captions to a Toolset gallery images.
Solution:
Toolset gallery block pulls the captions of the images from the WordPress Media Library. The caption needs to be added there, not inside the block.
