Understood - and indeed, to the best of my knowledge there is no way to do so via OOTB UI. Here are some alternatives I can think about (hint: development required).
If it is a "one-time" activitiy, my choices would both be related to scripting:
1. use the Groovy Console plugin (powerful, applicable for OnPrem or AMS only). You can query for the assets you need to update and perform the updates.
2. Perform the "bulk" export using the OOTB UI feature, then use scripting of your choice (e.g. python, bash etc.) to filter out the assets and perform the adjustments. (I do not think the csv would open in any editor app anyhow. )
If this is a more frequent occurence:
Consider creating a custom workflow which can run with a folderr as payload. A participant step selects the property name and value to filter out the assets, as well as providing the new property value. The next workflow step should take care of updating the relevant assets.
I know both ideas are not OOTB and I agree your use case would be interesting as an AEM feature. You can submit such an idea here https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager-ideas/idb-p/adobe-experience-manager-ideas