Maximo Open Forum

No, you can't have a single input tied to two attributes. I'm not entirely sure what you mean by conditional expressions in this context or how you would expect conditional UI to help but list tab/advanced search conditional UI is not really a thing as it can't evaluate the rules. 

The only way I could see something like this being possible is to build a custom view that has a single column for your two values. You mentioned model and catalog on items for example. So you could create a view that looks like this (replacing emxcatalog & emxmodel with the actual attribute names in your environment):

SELECT itemnum,itemsetid,emxcatalog as [modelcatalog] FROM item WHERE emxcatalog is not null
UNION
SELECT itemnum,itemsetid,emxmodel as [modelcatalog] FROM item WHERE emxmodel is not null

And then build a relationship from ITEM (on itemnum=:itemnum and itemsetid=:itemsetid) to this view and display the attribute as RELATIONNAME.modelcatalog. Maximo will build an exists SQL query that looks at this view to try and see if the item exists in this custom view. 

This would in theory work, but has the negative issue that you're no longer on the ITEM object for example. That means searching might be slower than if you were able to build the SQL on the ITEM object itself.

No, you can't have a single input tied to two attributes. I'm not entirely sure what you mean by conditional expressions in this context or how you would expect conditional UI to help but list tab/advanced search conditional UI is not really a thing as it can't evaluate the rules. 

The only way I could see something like this being possible is to build a custom view that has a single column for your two values. You mentioned model and catalog on items for example. So you could create a view that looks like this (replacing emxcatalog & emxmodel with the actual attribute names in your environment):

SELECT itemnum,itemsetid,emxcatalog as [modelcatalog] FROM item WHERE emxcatalog is not null
UNION
SELECT itemnum,itemsetid,emxmodel as [modelcatalog] FROM item WHERE emxmodel is not null

And then build a relationship from ITEM (on itemnum=:itemnum and itemsetid=:itemsetid) to this view and display the attribute as RELATIONNAME.modelcatalog. Maximo will build an exists SQL query that looks at this view to try and see if the item exists in this custom view. 

This would in theory work, but has the negative issue that you're no longer on the ITEM object for example. That means searching might be slower than if you were able to build the SQL on the ITEM object itself.