Great idea, sadly it disables any custom leader/civ.

Ooh. Neat!

Inspired by and based on the comment and work provided by Ciar Aon down below I released an extension for this EpsTweak: EPS Civ Picker Names Extension .
This mod adds several civilizations/leaders from other non-official mods provided by the community to this EpsTweak.

I can't get it specified correctly, the labels look unrecognizable.
LOC_LEADER_STR_UKRAINE_VOLODYMYR_ZELENSKYY_NAME_CONFIG_NAME_EPSTWEAK
<Update><Where LeaderType="LEADER_STR_UKRAINE_VOLODYMYR_ZELENSKYY_NAME"/><Set><LeaderName>LOC_LEADER_STR_UKRAINE_VOLODYMYR_ZELENSKYY_NAME_CONFIG_NAME_EPSTWEAK</LeaderName></Set></Update>

You'd need to go into the Core folder and alter the files there.

how is the leader zelensky's Ukrainian country of mod strudeler put on?

You'd have to add those manually to the mod files.

Does it work with modded civs added to the game?

@Eps, Eleanor of Aquitaine also needs a better solution (but my workaround works for English users for now). I also added like 65+ more custom civs and leaders, including almost everything from Gedemo. It's up on Google Drive if you want to pilfer the code for additional support. https://drive.google.com/drive/folders/1gCzFM5jQUGb39w4XLkYK38wzhZHl4lF4?usp=sharing

That would only work in English. I'd have to do some extra tinkering for the other ones.

Kublai Khan adds the country name after his name as well, so adding a new Leader name tag to your text file and then changing both Kubali Khan references to the new tag fixes the problem. Not sure how that'll work with translations, but it fixed it for me.

Example:
<Row Tag="LOC_LEADER_KUBLAI_KHAN_NONE_NAME" Language="en_US">
<Text>Kublai Khan</Text>
</Row>
<Row Tag="LOC_LEADER_KUBLAI_KHAN_CHINA_CONFIG_NAME_EPSTWEAK" Language="en_US"><Text>{LOC_CIVILIZATION_CHINA_NAME} - {LOC_LEADER_KUBLAI_KHAN_NONE_NAME}</Text></Row>
<Row Tag="LOC_LEADER_KUBLAI_KHAN_MONGOLIA_CONFIG_NAME_EPSTWEAK" Language="en_US"><Text>{LOC_CIVILIZATION_MONGOLIA_NAME} - {LOC_LEADER_KUBLAI_KHAN_NONE_NAME}</Text></Row>

Also, thanks for finally making a working Civ Selection mod since Sukritact's conflicts with YNAEMP.

Looks like it's fairly simple to add custom civs, just add a line to each of the two files with adjusted Civ and Leader tags.

Done. Now it should work with all of the game's languages.

Oh neat. I'll do that when I have the time.

another example: {LOC_CIVILIZATION_JAPAN_NAME} - {LOC_LEADER_HOJO_NAME}

for leader title there is also LOC_LEADER_BARBAROSSA_NAME

it's just an example of the german leader barbarossa

Yeah I tested it out. You have to do the following in your GameText.xml file:
<Row Tag="LOC_LEADER_BARBAROSSA_CONFIG_NAME_EPSTWEAK" Language="en_US"><Text>{LOC_CIVILIZATION_GERMANY_NAME} - {LOC_PEDIA_LEADERS_PAGE_LEADER_BARBAROSSA_TITLE}</Text></Row>

No, this is only for english names. But I guess I could pull the translated names from the database files at some point?

Does it work with different languages?