User parameter:
You can fill fields on screens with default values from SAP memory using parameter IDs. 
For example, a user only has authorization for company code 0001. By entering the value '0001' in field COCD in the Parameter register in this user’s master record (SU01), the system automatically fills the field Company code with the value ‘001’ on all screens he or she calls. If this company code is not predetermined using a parameter ID in the user master record, the system automatically adopts the first value entered by the user at the beginning of the transaction for the rest of the current terminal session. However, this value has to be re-entered the next time the user logs on to the system

Fields on screens are only ever automatically filled with the value saved under the parameter ID of a data element if the Set Parameter/Get Parameter attributes for the corresponding fields have been explicitly set in the Screen Painter.
Choose Tools -> Administration, then User maintenance -> Users. Enter the IDs you want in the Parameter register during user maintenance

How to create a new user parameter id , so that i can assign the same in SU01?

You can do in SE80, choose Other Objects, Enter name and Create.

If you want create paramenter id 'TEST' means:

STEP 1:
First add value 'TEST' in TPARA Table.

STEP 2 :
Assign value to paremeter id
DATA : LV_TEST TYPE CHAR10.
LV_TEST = 'TEST'.
SET PARAMETER ID 'TEST' FIELD LV_TEST.

To create a Parameter Id for a Data Element.

In se11 --> Data element name --> Futher Charactersitics -->
Parameter Id --> Type name example ZPARA --> Dbl click in it and create.

What are thses User parameter EFB & EVO? 
What is the full form of this?
When it is used?

Parameter IDs are used to ease the daily activities of a user.

For example:
If the user is responsible with one Purchasing grp/Pur Org/Plant then they adds WERKS/EKGRP parameter here, to have this Plant/Pur Group id filled when they calls the related transaction.
Parameter IDs are usually only used to memorize certain user-specific settings.  They can be included in the T code SU3 in the parameter tab.

EFB - This parameter id will define certain Purchasing authorizations
For one or more users. Here you can display certain user can display the conditions.

EVO - You assign default values that you have maintained in the Customizing to a particualt user by entering the key of the default value in the user master record under the parameter ID "EVO".

Relevant Topics:

• Basic System Navigation Question
• SAP R3 Transaction Codes
• SAP R3 Tables

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