Select custnbr 
from #plist
group by custnbr
having sum(case when prlist like 'pli%' then 1 else 0 end) = 1 and
    sum(case when prlist like '[ac]b%'...

Do you mean you can't use a SEQUENCE?  I can't imagine why.  I use those all the time when for whatever reason an identity is not appropriate.  And there's a...

First I would think would be to try this:

GRANT SELECT ON dbo.view_name TO [domain\account];

GRANT SELECT ON dbo.view_name2 ...

Use a table to store the date ranges, then join to that.

DROP TABLE IF EXISTS #DATES;
CREATE TABLE #DATES (
    VARIABLEA date NOT NULL,
 ...

You're also going to need to do something about the:

ar.Account_B__c as Account_ID,

a.SalesOrg__c as SalesOrg,

columns.  They are not in the GROUP BY and they are not within an aggregate function, so...

Best would be not to shrink the main db at all.  If possible, add a secondary filegroup, create the temp tables in there, then shrink only the file(s) in that...

You're good there, so that's not part of the issue.

Are you on the latest CU(patch-level)?

Have you verified that the threshold for parallelism setting is not too low?

Btw, neither "matched" nor "user_id" are SQL Server reserved keywords.

A trigger makes the most sense to me, so that the assignments are immediate.  You would also need a DELETE trigger to remove interested / mutual for a deleted user_id...

Btw, as noted by some others, I too, fortunately, have never seen any automated tool that can really properly analyze index usage and make really good suggestions for changes.  You...

SQL already captures the vast bulk of the stats you need, thus you don't generally have to set up separate runs, etc. to capture activity.

If you're willing to run the...

DECLARE @EndDate date
DECLARE @StartDate date

SET @StartDate = '20220101' --<<-- change @Start and @End values to get any date range you want
--get end of current month
SET @EndDate =...

Btw, you should always specify nullability (NULL / NOT NULL) when ADDing a column, otherwise it's extremely difficult to determine what you'll get there.

To get the last datetime for a given set of datetimes, you'd typically use ROW_NUMBER(), like this:

select ...
From (
    select *, row_numnber() over(partition by...