How to make an extension configurable through extension manager (TYPO3) - typo3

Question

I am currently developing my own TYPO3 extension (in v 9.5.11) and I would like to make some settings of my extension customisable. When I go to Admin Tools-->Settings-->Extension Configuration-->Configure Extensions, I can already change those settings.
However in earlier versions of TYPO3 (e.g. v7) it was possible to also make an extension configurable through Admin Tools-->Extensions-->"clicking the settings wheel of the desired extension" (see picture).
Where do I implement said function?

Answer 1

You simply define your desired settings in the file ext_conf_template.txt which needs to be stored in the root level of your extension.
The official TYPO3 documentation contains detailed instructions.

Answer 2

Like Michael said, you need to put all settings into the ext_conf_template.txt
Here is an example of my extension "slug" wich you can also find on Github or in the TYPO3 repository. It contains some special fields and even translations.
# Settings
###########################
# cat=defaults; type=options[10,20,30,40,50,60,70,80,90,100,150,200,300,400,500]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:default.maxentries
defaultMaxEntries = 20
# cat=defaults; type=options[crdate,tstamp,title,slug,sys_language_uid,is_siteroot,doktype]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:default.orderby
defaultOrderBy = crdate
# cat=defaults; type=options[DESC,ASC]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:default.order
defaultOrder = DESC
# cat=defaults; type=boolean; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:default.recordInfoEnabled
recordInfoEnabled = 1
# cat=tree; type=boolean; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:tree.enabled
treeEnabled = 1
# cat=tree; type=options[1,2,3,4,5,6,7,8,9,10]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:tree.depth
treeDefaultDepth = 3
# cat=tree; type=string; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:tree.root
treeDefaultRoot =
# cat=custom records; type=boolean; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:record.enabled
recordEnabled = 0
# cat=custom records; type=options[10,20,30,40,50,60,70,80,90,100,150,200,300,400,500]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:record.maxentries
recordMaxEntries = 10
# cat=custom records; type=options[crdate,title,path_segment,sys_language_uid]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:record.orderby
recordOrderBy = crdate
# cat=custom records; type=options[DESC,ASC]; label=LLL:EXT:slug/Resources/Private/Language/locallang_be.xlf:record.order
recordOrder = DESC
And here is how I use the settigs in any Controller I want:
<?php
use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Core\Configuration\ExtensionConfiguration;
class ExtensionController extends \TYPO3\CMS\Extbase\Mvc\Controller\ActionController {
public function __construct() {
$this->backendConfiguration = GeneralUtility::makeInstance(ExtensionConfiguration::class)->get('slug');
}
public function myRandomFunction(){
$variable = $this->backendConfiguration['recordMaxEntries'];
}
}
This is how it looks: