Hi @zameer_abbas
Can please cross check whether you have included "misctools#sourceedit" in toolbar property list, adding this will enable source edit option. if you have already included this & still if its not visible then please share dialog.xml screenshot/code snippet.
<uiSettings jcr:primaryType="nt:unstructured">
<cui jcr:primaryType="nt:unstructured">
<inline
jcr:primaryType="nt:unstructured"
toolbar="[format#bold,misctools#sourceedit]">
<popovers jcr:primaryType="nt:unstructured">
</popovers>
</inline>
<dialogFullScreen
jcr:primaryType="nt:unstructured"
toolbar="[format#bold,misctools#sourceedit]">
<popovers jcr:primaryType="nt:unstructured">
</popovers>
</dialogFullScreen>
</cui>
</uiSettings>
-Manjunath