Chrome Version: 60.0.3112.52
Chrome OS Version: 9592.42.0
Chrome OS Platform: samus

When choosing Dayi (大易, one of Traditional Chinese IME), when a character composition has more than one candidates, it has no keyboard selection mechanism.

Steps To Reproduce:
(1) Use Dayi IME
(2) Type 'v' symbol, it brings three candidates 1.夫 2.大 3.禾
(3) You can pick the first one by pressing "space", which is expected.
(4) However, you cannot pick the second or third candidates by typing '2' or '3', which is treated as the second symbol to compose a character.
(5) Now you can only select candidate using mouse, which make the IME unable to use in real world case.

Expected Result:
By the original design of DAYI IME, you have to press <space> to submit character composition to show up the candidate list. And the candidate selection key is 
1. <space> 
2. <'> 
3. <[>
4. <]> 
5. <-> 
6. <\> 
7. <shift> + <'>
8. <shift> + <[>
9. <shift> + <]>
10. <shift> + <->
For the case of 'v' input, here is the expected type sequence:
大 <v> <space> <space>
夫 <v> <space> <'>
禾 <v> <space> <[>

There is a variant of DAYI candidate selection, it automatic composes symbols if the sequence can map to candidate(s). For this variant, you can save the first <space>, which means "submit the symbol sequence to compose". For this variant, the candidate selection sequence becomes (shifted by one compared to original):
1. <'> or <space>
2. <[>
3. <]> 
4. <-> 
5. <\> 
6. <shift> + <'>
7. <shift> + <[>
8. <shift> + <]>
9. <shift> + <->
10. <shift> + <\>

Actual Result:
<v> <1> it is composed as 千
<v> <2> it is composed as 犁 
<v> <3> it is composed as 看

However, using the candidate selection key of the variant works:
<v> <space>: 大
<v> <'>: 大 
<v> <[>: 夫
<v> <]>: 禾



How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?) Always

What is the impact to the user, and is there a workaround? If so, what is
it?
Impact for Traditional Chinese user who uses DAYI IME. Not sure the population of DAYI user. But since it should be a long lasting bug, DAYI user may find some alternatives.

Please provide any additional information below. Attach a screen shot or
log if possible.

The solution should be quite straight forward: change the candidate list's 1 2 3 to the candidate selection symbol, ' [ ]. 
A even better solution is to provide an option for user to select candidate selection rule, either the first one (need a space to send symbol(s) to compose) or the second variant (auto show candidates for current symbol(s), but with candidate selection symbol shift by one).