I guess the problem is this (if you visit one of the categories)

https://mnw.wiktionary.org/wiki/Category:%E1%80%9D%E1%80%B1%E1%80%AB%E1%80%9F%E1%80%AC%E1%80%A1%E1%80%9D%E1%80%BA%E1%80%83%E1%80%BE%E1%80%B3%E1%80%9A%E1%80%BB%E1%80%AC%E1%80%94%E1%80%B1%E1%80%90%E1%80%BA-%E1%80%A1%E1%80%81%E1%80%AD%E1%80%AF%E1%80%80%E1%80%BA%E1%80%80%E1%81%9E%E1%80%AC%E1%80%82%E1%80%BD%E1%80%B6%E1%80%9C%E1%80%9D%E1%80%BA%E1%80%A1%E1%80%AC%E1%80%B2%E1%80%80%E1%81%9F%E1%80%AC%E1%80%B2%E1%80%94%E1%80%B0%E1%80%9D%E1%80%B1%E1%80%AB%E1%80%9F%E1%80%AC%E1%80%99%E1%80%AC%E1%80%9C%E1%80%AC%E1%80%9A%E1%80%9D%E1%80%BA-%E1%80%95%E1%80%9D%E1%80%BA%E1%80%9C%E1%80%B3%E1%80%94%E1%80%B3%E1%80%83%E1%80%BE%E1%80%B1%E1%80%94%E1%80%BA%20%E1%80%9C%E1%80%B9%E1%80%95%E1%80%AC%E1%80%BA%E1%80%96%E1%80%AC%E1%80%97%E1%81%9F%E1%80%B6%E1%80%80%E1%80%BA-%E1%80%A1%E1%80%81%E1%80%AD%E1%80%AF%E1%80%80%E1%80%BA%E1%80%80%E1%81%9E%E1%80%AC%E1%80%82%E1%80%99%E1%81%A0%E1%80%AD%E1%80%AF%E1%80%84%E1%80%BA?uselang=en

The requested page title is too long. It must be no longer than 255 bytes in UTF-8 encoding.

As you said, I can't create a category, thanks.

And you asked what the issue is. The page itself tells you the error.

The issue is the title is too long (primarily due to the number of bytes that the characters require being > 1 per character)...

The simplest workaround for now, is unfortunately to use a shorter title for the category.

Every Proto-Central-Eastern Malayo-Polynesian name pronunciation was written in the Mon alphabet, but I don't understand any of these, I used the Mon alphabet as it was originally pronounced, Please let me know if there is any other alternative name for the Proto-Central-Eastern Malayo-Polynesian name, I have exchanged it with the original pronunciation of the Mon alphabet as follows.
Proto=အခိုက်ကၞာ
Central=ဗဟဵု
Eastern=လ္ပာ်ဖာဗၟံက်
Malayo=မာလာယဝ်
Polynesian=ပဝ်လဳနဳဃှေန်
I am a writer and I can guarantee my knowledge, what should I do next?

I'm currently the only one working on Mon Wiktionary, so please help me with the technical stuff, thanks.

Hi, please see https://meta.wikimedia.org/wiki/Small_wiki_toolkits for help. Thanks.

It's not the same issue as T275319: Change $wgMaxArticleSize limit from byte-based to character-based/T308893: Increase $wgMaxArticleSize to 4MB for ruwikisource, but a similar underlying cause.

I would've presumed a generic task for title length existed, but I can't find one offhand.

When we use the Mon alphabet to pronounce the names of other languages, we will not see abbreviations in English languages, but long names. as an example, we can look at the full name of King Manuha, Also, all the powerful people in our nation have long names, but I also have long names, so I would like to request that a long name be added to the Mon language wiki, thanks.

In T325650#8482147, @Intodesa wrote:

Also, all the powerful people in our nation have long names, but I also have long names, so I would like to request that a long name be added to the Mon language wiki, thanks.

I've filed T325665: Increase title length as a more generic request, as if we do it for one wiki (because it's a database schema change), we really need to do it for all wikis.

It's a lot of work for our DBA's, so it is unlikely to be completed anytime soon.

Thank you