How to display of all routings for all materials at a time?

Try Standard TCode CA51, if not suitable for your requirement then you can create customized report (Z TCode) or Query.

See the below table relationship:

Please ask your ABAPer to create the report with the following tables:

Table MAPL, pass input material number, plant, routing group counter. 

Table PLKO, field PLNNR, PLNAL eq mapl-plnnr, mapl-plnal 

Table PLAS, field PLNNR, PLNAL eq mapl-plnnr, mapl-plnal and LOEKZ ne ' ', take field PLNKN 

Table PLPO, field PLNNR, PLNKN eq plas-plnnr, plas-plnkn 

You will get correct result same as CA03 list. 

Routing Table’s

PLPO          Routing Operation Details
PLKO         Routing Header Details 
MAPL         Routing Link to Material 
PLAB          Relationships - Standard Network 
PLAS          Task List - Selection of Operations 
PLMZ         Component Allocation 
PLPH          CAPP Sub-operations 
PLFH          PRT Allocation 
PLWP         Maintenance Package Allocation 
PLMK         Inspection Characteristics

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