In tt_content I added a new field in my sitepackage. Purpose: Add a css-class in the rendered content element. Now I have the problem how to get the value of this field into the typoscript setup.

# Get value for frameAttributes from field tx_dta_site_shadows in tt_content
lib.shadowSettings = COA
lib.shadowSettings {
    10 = TEXT
    10 {
        data = field:tx_dta_site_shadows
    }
}

# Extend frameAttributes typoscript from bk2k/bootstrap-package in sitepackage
lib.contentElement {
    dataProcessing {
        1682424577 {
            data {
                    class < lib.shadowSettings.10.data
                }
            }
        }
    }

The rendered result is:

<div class="field:tx_dta_site_shadows frame frame-default etc...>

But it should be:

<div class="my-shadow-classname-from-tt-content-field frame frame-default etc...>

Can you point me in the right direction?

In use: Typo3 v12.4.16 with bk2k/bootstrap-package