If you have a need to assign particular bolts and/or gaskets to specific flanges in your specs, this can be accomplished using the Bolt (and Gasket) Selection Code as well as Bolt Designator for visual reference in your models.
In this case perhaps you have some bolts that are to be optional items because they are supplied by others.

You can accomplish the desired goal of getting the right bolts and gaskets with the right flanges by using the Bolt & Gasket designation(s) with your flanges.

Keep in mind that this will require a little "tweaking" of your catalog data tables up front.

In your catalog you will need multiple bolt, gasket & flange tables to accomplish this. Here is an example of a bolt table where the Selection Code has been entered, and the Bolt Designator has a value as well. This particular table is set to be Optional by default.

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Next, in my spec I have multiple bolts, each looking at a different bolt table in the catalog. This particular bolt is set to the table described earlier.

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For the flanges that will use the matching bolt set (notice that the flange table name resembles the bolt table to make it easier to remember). The applicable bolt is set using the drop-down.
Notice that the bolts are optional items but the flange is not.

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When that bolt is placed in the model, the Optional component dialog comes up to verify....

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And the Bolt Designator values becomes visible.

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