Is it possible to enter text as if normal Chinese text is entering
i.e. with guessing of correct characters, but later entering Pinyin of entered text, not characters themselves?
Usual IME's won't have that feature... so I think you have two approaches here.
Almost all IME support symbol insert
Test Which method your IME support
Switch to Chinese IME, type 'v', if you see some special candidate words, then your IME support that, just follow the instructions. On my IME, it is English Mode, not very useful.
Type 'i', as before, just follow the instructions. On my IME, it is the number mode. ①,二, ⅲ, ⑷, ➎, 陆, ㈦
Type 'u', on my ime, it is command mode.
Open settings of your IME, click '短语设置' or '快捷短语 or similar names, it may be in 高级设置 or 自定义设置 page.
You will see a long list (it you can't see it, click 查看 or 编辑...), Every line in the list is formed by a code and a word, you can use that code to input the matched word quickly.