UPDATE: It's possible to use the following syntax to check for an attribute-value, regardless of which attribute has that value:

where attrvalue = 'some_name'

It's also possible to combine these with OR to match one of several values:

where attrvalue = 'some_name' or attrvalue = 'other_name'

However, combining these with AND does not work to match two different values of two different attributes.

Also, the following works as expected (note the use of OR between parantheses) :

where (attribute = 'attr1' and attrvalue = 'some_name') or (attribute = 'attr2' and attrvalue = 'other_name')

However, the following does not work as one would want (note the use of AND between parantheses) :

where (attribute = 'attr1' and attrvalue = 'some_name') and (attribute = 'attr2' and attrvalue = 'other_name')

The exact syntax and limitations of the cm find command remains a mystery... It is not very consistent, unfortunately.

I added the request for branch depth/level support in "find branch" as a separate uservoice here:
https://plasticscm.uservoice.com/forums/15467-general/suggestions/13071576-add-support-for-branch-depth-in-find-branch-comman

I added the request for branch namespace support in "find branch" as a separate uservoice here:
https://plasticscm.uservoice.com/forums/15467-general/suggestions/13071435-add-support-for-namespace-in-find-branch-command
Please vote for it if you care about this...

UPDATE: The following command actually works (at least in 5.4.16.731) for finding all the branches that do NOT have the specific attribute "branch_status" applied (regardless of whether there are other attributes or not) :

cm find branch where not attribute = 'branch_status'

(Note the use of "not" instead of "!=" in this query...)

To filter the Branches view for branches that do NOT have a specific attribute for our "branch_status" attribute, I can use the following syntax:

find branch where attribute="branch_status" and attrvalue != "completed"

However, that will NOT include branches that don't have that attribute applied at all. It would be much more useful if there was a way to include these too in the same query.

To find the branches that don't have the attribute applied, it would be logical to use the following syntax:

find branch where attribute != "branch_status"

That query works, but not as expected. It has a very counter-intuitive interpretation: [where (count attributes > 0) AND (attributes DO NOT CONTAIN 'branch_status')].

Please consider changing the interpretation to simply: [where (attributes DO NOT CONTAIN 'branch_status')].

Additionally, finding a branch by namespace is not possible. Even worse, [find branch where name = 'main'] returns 1 branch, but [find branch where name = '/main'] returns none! Please add full namespace support so we can find branches by complete name such as name = '/main/task001/subtask_1'.

Also, I propose adding a "depth" or "level" filter-option for the branch find-object, to filter on branch namespace-depth (like "Display branch levels" in Branch Explorer).

Yeah. That's what I was asking for here: http://www.plasticscm.net/index.php?/topic/2002-find-changesets-where-a-specific-attribute-is-not-set/?hl=%2Bfind+%2Battribute

Also, a way to find all branches etc where a specific attribute is NOT applied.