Lightroom: The tagging system on CC does not work as it should.

Hello David,

That sounds frustrating. I tried to duplicate what you are seeing but wasn't able to.  Can you provide detailed step by step instructions that will cause the bad behavior in a repeatable manner? Are you running the Lightroom CC 1.5 version? (Help>System Info...)

ON 1.5 seems fine for add or remove tags but : 
Are tags embedded in file or not?
When I want to tag, there is no list of tag already created. So there is a risk of creating for example a case sensitive tag?
I'm not sure tags are sync between classic and CC

I think I got all the question marks here...

Tags are not embedded in the file but rather, in the Lightroom CC Catalog which lives on all your Lightroom CC devices, desktops and the web.  These tags sync across the Lightroom CC ecosystem. 

At this time there is no list of tags available like there was in Lightroom Classic CC. 

Tags do not sync between  Lightroom CC and Lightroom Classic. 

I see there is an another topic https://feedback.photoshop.com/photoshop_family/topics/keyword-bug

It is really strange or at least no understandable that if we want to protect (is cloud a real protected backup not sure in fact) or work in cloud, so much feature are not implemented. If I decide not to work anymore on classic and only on CC, I can't embed tag. Resulting I'm stuck in adobe ecosystem and the day I decide to not use anymore LR CC because too expense, no roadmap or no basic feature (export, print...), I will have to input once again tags. 
Thats crazy and unfair