Disable post title escaping

What is the role of the user you are trying to use? And which editor are you using to edit the titles?

The background to the question is explained in this section of an article: https://make.ww.wp.xz.cn/core/handbook/contribute/design-decisions/#unfiltered-html-for-editors-administrators-multisite

Yes, the block editor (Gutenberg) escapes titles for all users. AFAIK disabling this is not practical. I suggest as a workaround you use the Quick Edit feature from the post/page list table.