Typoscript Condition: backend_layout (with slide) - typo3

Question

I use this condition
[globalVar = GP:colPos==0]&&[page|backend_layout = pagets__MainTemplate]
My problem is that my „subpage“ has no backend_layout selected because the parent pages "Backend Layout (subpages of this page)“ is set. So the condition does not work on subpages.
Can create a condition like that?
lib.backendLayout = TEXT
lib.backendLayout {
data = levelfield:-1, backend_layout_next_level, slide
override.data = TSFE:page|backend_layout
}
I want do white/blacklist CTypes in BE Columns in this way:
[globalVar = GP:colPos==0]&&[page|backend_layout = pagets__MainTemplate]
TCEFORM.tt_content.CType.keepItems := addToList(header)
[end]

Answer 1

Not as far as I know, as you can only access the current page record with the "page" condition.
Instead you could
a) Write your own condition (see https://docs.typo3.org/typo3cms/TyposcriptReference/8.7/Conditions/Reference/Index.html#custom-conditions or starting with version 9 https://docs.typo3.org/typo3cms/TyposcriptReference/Conditions/Reference.html#extending-the-expression-language-with-own-functions-like-old-userfunc)
b) Use a userFunc (like "a" only older and less fancy ;)) - see https://docs.typo3.org/typo3cms/TyposcriptReference/8.7/Conditions/Reference/Index.html#userfunc
new c) follow Jigals suggestion (or use a similar extension - there are a few - but they mostly do a lot more than what you need)
--- EDIT after question update ---
As you want it working in TSConfig c) is actually not an option.
c) depending on what you actually want to achieve with your condition use if and data (like in your description) directly at the TS objects that should have different behavior if your condition is true.
For reference:
Differences between TSConfig Conditions and TS Conditions:
https://docs.typo3.org/typo3cms/TSconfigReference/8.7/Conditions/Index.html#differences-to-conditions-in-typoscript-templates

Answer 2

As an alternative to Susi's solutions you could use Gridelements. This extension has the feature that you can set inside each block in a backend layout which CEs are allowed.