I was going to request, what I think, is this same feature. OP is a little more vague, and the feature request guide says to be specific. I also see that several people have created feature requests that have been merged into this one. This was going to be my feature request:
Dynamic cross-item referencing/linking
Request
Ability to link values to another items value, so the value would almost act as a variable
What would this look like?
When setting the value for custom fields, or perhaps even a new item type of “Linked Item” you could select another items value. You cannot change the value from this link. Selecting the value would instead link you to the referenced item where you could change it there. The value does not even have to show the actual value, but can simply be a link to where it will pull the value from. In an organization, the user would have to have access to both items to see/use the value.
Why do we need this?
This helps keep it DRY (don’t repeat yourself). This can be used in any number of circumstances where users may need to change two or more values to the same thing, but they would have to change each one individually.
Examples
I have a school account where blackboard uses the portion without the @school.edu portion of the email, but the password is linked to the email account. I have two login items, one for the email and one for blackboard, but the passwords are always the same. If I change the password, I need to change it in both places for it to be correct. If this were implemented, I would instead link the blackboard password to my school email password where I would now only need to change it once.
In an organization, if you wanted to utilize Bitwarden for secure notes, you could include what key accesses what rooms. I may want to have a list of rooms, and what key is used to get into that room. I would also like to include what key ring number that key can be found on. If key #10 gets into five different rooms, I could have a listing for each room that says key #10 is on “Key Set 2”. Let’s say we re-organize, now key #10 is moved to “Key Set 3” I now have to go to all five listings to remember to change them. Instead, I could have a separate item that has the information about the key #10, and on each room that uses that key, I would have a custom field that links to that item created for key #10. Clicking that link would bring you to that item. Now that we are able to link to items, I could include a link to that item in the note or custom field, but it is not a clickable hyperlink. The user would have to copy and paste it into their browser, and especially on mobile phone is rather impractical.
This feature request has had similar iterations, but I think this solution would be wide reaching.