Hi, I am using multiple tabs in my form. I need to display certain bu

Why not just break this into two chained forms with the appropriate buttons displayed on each form?

The user likes to see all the part in one form. Since it is a very long form, it has been split into tabs. So I have to maintain the tab design. Is there any other workaround?

Buttons can be placed either on the bottom, or top and bottom of a form. Depending on your use case, Larson's workaround might be best; you can split the tabs into different forms and take advantage of activity chaining to go back and forth.

forum.appian.com/.../Button_Field_Input
forum.appian.com/.../Configuring_Activity-Chaining

Can you elaborate on your use-case? Are the values that are currently shown in the first tab supposed to be editable, while the values currently shown in the second tab supposed to be read-only? What is supposed to happen if the user clicks the "Edit" button? Is the user able then to edit the values currently shown in Tab#1 AND Tab#2?

Use case is as follows: The form contains many fields but in different sections. The user likes to see each section in different tabs. The "Edit" button will lead to another form but correlated with tab 2. Since is "Edit" functionality is logically related to tab 2, the user will like to see that button only in that tab.

The button does not change the values in tabs. It will take to another form.

@Bishnu - Already there are other forms in the use case that be chained.

There is a way you can do this with Javascript. You can add an image to the page. And add an on click event which submits the form button. You can then use javascript on the button to hide it from view. Something like:
On the image:
On mouse up
getObject('buttonValue').parentNode.firstChild.click();

Then hide the button with
window.FormAPI.hide("buttonValue");
Obviously Appian would recommend not using javascript and would advise the OOTB functionality of chained forms but if you really need the buttons in the tabs this may just help.