Custom tags and labels can be added to cloud instances using the special Power Tags !CLOUDTAGS and !CLOUDLABELS respectively. During instance creation, the company account's Power Tags are taken into account, as well as the new instance's cluster in case of an elastic clone. Hence, these PowerTags need to be set either on the cluster's or company settings page.
In the following example, the following company-wide Power Tags were set:
!CLOUDTAGS=allow-44300;allow-8080
!CLOUDLABELS=extratag1=test;extratag2=test;extratag2=test
Resulting in this: