Subject heading pretty much says it all... Is there any way to add a disclosure triangle to a layout?

It's not too hard to have a button that switches layouts, switches tabs, sets a value to show a calculated result, or sets a key to show a hidden portal row. Any of those can have a similar effect as Apple's disclosure triangles.

Maybe I should expand on what I want. Suppose I'm looking at a set of records in "list" view. The layout shows just some bare info about each record. I want to be able to see more details about one single record. In my mind I click on a disclosure triangle, and that one record 'expands' to show more details, with the other records shifting down to make space for them.

The methods you propose couldn't be used to produce this effect, could they?

Is it possible to have a layout part that appears or disappears based on a calculation? That would also get me where I want to go.

In a list view, each record in the Body will be the same size (while browsing anyway). But you can get a similar result by employing the Header or Footer for the record's detail information. See Stephen's example here (it helps to have FM9)

http://www.fmforums.com/forum/showtopic.php?tid/190057/

Is it possible to have a layout part that appears or disappears based on a calculation? That would also get me where I want to go.

Not in Browse Mode.