I found a way to know hidden customizing Tcodes.

Before executing customizing task you desire, point it and go to Edit-Display IMG Activity. Then mark activity.

Go to T.Code se16 and type in CUS_IMGACH table.
Execute.
Paste IMG Activity and run.
You will see Tcode that belongs to IMG Activity.

SAP SD Tips by: Javier

The most frequently used transaction codes are as follows:
1. VS00 - Master data
2. VC00 - Sales Support
3. VA00 - Sales
4. VL00 - Shipping
5. VT00 - Transportation
6. VF00 - Billing

Others as follows:
At Configuration:
1. VOV8 - Define Sales documents type (header)
2. OVAZ - Assigning Sales area to sales documents type
3. OVAU - Order reasons
4. VOV4 - Assign Item categoreies(Item cat determination)
5. VOV6 - Scedule line categories
6. OVAL - To assign blocks to relevant sales documents type
7. OVLK - Define delivery types
8. V/06 - Pricing
9. V/08 - Maintain pricing procedure
10.OVKP - Pricing proc determination
11.V/07 - Access sequence

Enduser:
1. Customer Master Creation-VD01 and XD01 (for full inclu company code)
    VD02 - Change Customer
    VD03 - Display Customer
    VD04 - Customer Account Changes
    VD06 - Flag for Deletion Customer
    XD01 - Create Customer
    XD02 - Modify Customer
    XD03 - Display Customer
2. Create Other material ----MM00
3. VB11- To create material determination condition record
4. CO09- Material availability Overview
5. VL01 - Create outbound delivery with ref sales order
6. VL04 - Collective processing of delivery
7. VA11 - Create Inquiry
    VA12 - Change Inquiry
    VA13 - Display Inquiry

Sales & Distribution
Sales order / Quote / Sched Agreement / Contract
· VA01 - Create Order
· VA02 - Change Order
· VA03 - Display Order
· VA02 - Sales order change
· VA05 - List of sales orders
· VA32 - Scheduling agreement change
· VA42 - Contract change
· VA21 - Create Quotation
· VA22 - Change Quotation
· VA23 - Display Quotation

Billing
· VF02 - Change billing document
· VF11 - Cancel Billing document
· VF04 - Billing due list
· FBL5N - Display Customer invoices by line
· FBL1N - Display Vendor invoices by line

Delivery
· VL02N - Change delivery document
· VL04 - Delivery due list
· VKM5 - List of deliveries
· VL06G - List of outbound deliveries for goods issue
· VL06P - List of outbound deliveries for picking
· VL09 - Cancel goods issue
· VT02N - Change shipment
· VT70 - Output for shipments

General
· VKM3, VKM4 - List of sales documents
· VKM1 - List of blocked SD documents
· VD52  - Material Determination

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