[Optimization] During the construction of the query, the variable names should be prompted into the drop-down list

[IvanGao01]

As the image shows, the variable $host should be prompted in the drop-down list

[zipper-meng]

What is your opinion about the view of the dropdown tag values list when a tag value exists in variables and not in metric query results?

If host variable (defined in grafana) has values [hostA, hostB, hostC], while the metric query (exists in database) has values [hostC, hostD, hostE], the dropdown list would be like:

• hostA (grey or strikeout)
• hostB (gray or strikeout)
• $\underline{hostC}$ (underline)
• hostD (normal)
• hostE (normal)