Problem:

When users with a role lower than administrator log-in the following fatal error may occur with "Enable Media Replace" plugin.

Solution:

It is a known issue, see our erratum here:

https://toolset.com/errata/fatal-access-error-when-non-admins-log-in/

Relevant Documentation:

Problem:

How to connect the parent/child posts in the child post form?

Solution:

In the single parent post, you can get the current parent post ID with shortcode:
[wpv-post-id item="$current_page"]

And use above shortcode as default value of relationship field of child post form.

Relevant Documentation:

Problem:
Custom Marker for each category (Taxonomy)

Solution:
To display different marker based on different taxonomy terms while using blocks, you will have to add conditional block and within conditional block you will have to add the "Fields and Text" block that should hold the marker shortcode.

You can find proposed solution in this case with the following reply:
https://toolset.com/forums/topic/custom-marker-for-each-categorie-taxonomy/#post-2329289

Relevant Documentation:
=> https://toolset.com/documentation/programmer-reference/maps/maps-shortcodes/#wpv-map-marker
=> https://toolset.com/course-lesson/using-toolset-conditional-block/