Idea Summary
The docs.oracle.com Apex documentation, release notes, and the Apex Page Designer contextual help tab should give the APEX_DICTIONARY view and column for the attribute being described.

For example: Select a page item the page designer, focus on Identification → Type in the property editor, open the help tab. It should mention that the this value is found in APEX_APPLICATION_PAGE_ITEMS in the columns DISPLAY_AS and DISPLAY_AS_CODE.

Use Case
When migrating between versions of Apex the Release notes lists deprecated and desupported features.

Migration cannot always provide a like for like alternative so it can be necessary to find where features are being used before and after migration.

I think the quick way to do this should be to use the views from APEX_DICTIONARY to check where a particular feature is used.

My examples are from preparing to migrate a 21.2 setup to 22.2 so are based on reading the release notes for 21.2, 22.1, and 22.2.

Example 1: Release Notes 22.1 Section 8.1.6 desupports “Post Calculation” for page items.

I don't know of an option by this name.

Searching the docs for “Post Calculation” only brings up the release notes with no other results:

After searching forums.oracle.com for the same I'm reasonably confident this is referring to Post Calculation Computations. I am familiar with this and see discussion of it's deprecation but this is now a best guess instead of a certainty.

I look at the views available in APEX_DICTIONARY filtering for column names like ‘%CALC%’ but get no results.

Checking for ‘%POST%’ gives a few results. I find APEX_APPLICATION_PAGE_ITEMS has the column SOURCE_POST_COMPUTATION. The description does not mention Post Calculation, or Post Calculation Computation, but I'm pretty sure this is it.

I'm now reasonably certain this refers to the thing, which I'm reasonably certain refers to the thing that is being desupported.

Querying the view and column to check if any apps are using it takes seconds.

The different naming is an annoyance but if the release notes and the page designer help gave the view and column then they would link up. All the uncertainty would be gone and the majority of time taken would be saved.

Example 2: Release Notes 22.1 Section 6.1.6 deprecates Region Image and Image Tag Attribute in the property editor. Release Notes 22.2 Section 8.1.2 desupports them.

I know these options. I searched the region views I know of and checked column names.

None look right but I see generic attr_xx columns which I guess could contain the values.

I set Region Image to “region_image_value” and Image Tag Attribute to “image_tag_attribute_value” on a region in a test app and then inspect the views filtering to the region ID to try and find those values but could not.

I then searched APEX_DICTIONARY for all views with a column like ‘%REGION_ID%’.

I export all the data from those views filtering to the region ID but still couldn't find the values.

I then exported the app to an SQL file and find the procedure wwv_flow_api.create_page_plug has properties p_region_image and p_region_image_attr with the values.

I used a PL/SQL script to dump all the Apex application exports line by line into a table. I was then able to search the table for those properties to see if any other app was using them.

If the release notes advised of the view and column to  check this would have been a significant time saving.