That is the problem of TyperRacer, not the IME or you. I suggest you using platforms created by Chinese speaking people, which could be optimized for Chinese practice.
For example https://dazi.kukuw.com/keyboard.html
In pinyin erhua is usually written with a natural tone:
哪儿, like you mentioned above, for example is written:
Erhua is tacked on to the end of the pinyin and the tone is in the usual place for the preceding character.
An easier way to see this is probably for a word like 瓶儿. 瓶儿 is written:
The erhua is not merged into the pinyin (like you ...
1, You can use the software "Auto-hot-key"
Create a script and add the following lines
Run the scripts.
When you type [ on the keyboard it will be 「. When you type ] it will be 」. This solution will work regardless of Input Methods. This is neat and the most recommended solution.
You can also use different hotkeys, with or without ...