If I understand you, you can check if the admin page is being accessed by checking the $ACT value using the
action_act_preprocess[/m] event: https://www.dokuwiki.org/devel:event:action_act_preprocess. If $ACT =='admin', set a boolean to this effect, for instance: $this->isAdmin = true. Then if $this->isAdmin is true when the [m]TPL_TOC_RENDER handler is called, proceed as required; you can just return without processing the event.
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Edit:
https://www.dokuwiki.org/devel:action_modes