Replicate the "Group Members(sys_user_grmember.group)" related list on Group form for a custom table

[Mudabir]

I have a custom table ( Custom 1) with two reference fields 
1. Group field ( Reference to Group table)

2. Issue  field ( Reference to a different custom table (Custom 2))

On the Group form I want to show a Related List that shows the records from Custom 1 table ( which is pretty straight forward)
I want "Edit" button on this related list. But when the "Edit" button is pressed, on the left side of the slush bucket it should show records from Custom 2 table. Just like for ""Group Members" related list, this related list shows user records on the left side of slush bucket when "Edit" is pressed.

Thanks!

[JenniferRah]

Why would you make it between Group and Custom 1? I thought the goal was to have related records between Custom 1 and Custom 2?

[Mudabir]

@JenniferRah  The goal as stated in the description is to create a Related List b/w Group & Custom 1, show it on Group. The "Edit" button should show the records from Custom 2 on the left side of slush bucket. Similar to sys_user_grmember.group related list on Group.

[JenniferRah]

An m2m table relates one kind of record to another. So if you are relating Groups to Custom 1, then Custom 2 has nothing to do with anything. If you want the values from Custom 2 to show in your related list, then the relation is between Custom 2 and Group. 

Think about the sys_user_grmember table that you mentioned: It's a relationship between Groups and Users.

• When you add it to the Group table, it shows Users.
• When you add it to the User table, it shows Groups.

[Mudabir]

@JenniferRah 
I took the m2m route because it was suggested on many forums.

True what you said about sys_user_grmember table. But see, as you would already know, the Group Members (sys_user_grmember.group) related list, it shows the records from User table and not from the sys_user_grmember itself. This is exactly what i want to replicate.
A related list on group (custom_1.group) showing records from Custom 2 table.

[JenniferRah]

custom_1.group is not a record, it's a field. If you want it to show on the Custom 1 record, you will need to relate it to the Custom 1 record. 

Using an M2M table is the only way to get the slush bucket functionality that you are looking for. 

I guess I'm not seeing the use case for what you are describing. You can filter the choices in the Issue field (Custom 2) based on the group selected, if you have a group field in the Custom 2 table.