So we have 2 Account objects. The standard one Account, and a custom one called Wholesale Account. (yeah, I know this is not really the best design but we are kinda stuck with it.)

We added Opportunity as a child of the custom object, but it still wants to always have an Opportunity connected to an Account. Is there some way to make an Opportunity that is attached to something other than a standard Account object?

Either by creating a new field on an object using Setup->Fields & Relationships or Schema Builder, I have to refresh the page many times or even log in and out, for the field to actually be visible on the user interface (i.e. tab/object on the sales app).

After a few minutes, it appears (so it has nothing to do with the visibility permissions).

Does it take that long for the database to be reached by the user interface or what could be the problem?

Using: Chrome / Lightning Experience / Development Edition or Playground