Changes
transclude if exists only, use edit link otherwise, because it gives preload
<span class="editsection plainlinks" id="doc_editlinks">[[{{fullurl:{{{1|{{SUBJECTPAGENAME}}/doc}}}|action=edit{{#ifexist: {{{1|{{SUBJECTSPACE}}:{{SUBJECTPAGENAME}}/doc}}} ||&preload=Template:Documentation/preload}}}} edit]]</span>
<span style="font-size: 150%">{{{heading|Documentation}}}</span></div>}}
<div id="template_doc_page_transcluded" class="dablink plainlinks">This [[Wikipedia:Template documentation|documentation]] is [[Wikipedia:Transclusion|transcluded]] from [[{{{1|{{FULLPAGENAME}}/doc}}}]].'' <small>([[{{{1|{{SUBJECTPAGENAME}}/doc}}}|view]] | [{{fullurl:{{{1|{{SUBJECTPAGENAME}}/doc}}}|action=edit{{#ifexist: {{{1|{{SUBJECTSPACE}}:{{SUBJECTPAGENAME}}/doc}}} ||&preload=Template:Documentation/preload}}}} edit] | [{{fullurl:{{{1|{{SUBJECTPAGENAME}}/doc}}}|action=history}} history])</small> {{#ifexist: {{#rel2abs: /sandbox }} | {{#ifexist: {{#rel2abs: /testcases}} | <br> ''This template has a [[/sandbox|sandbox]]'' <small>([{{fullurl:{{FULLPAGENAME}}/sandbox|action=edit}} edit])</small> ''and [[/testcases|testcases]] for editors to experiment.''}}<!-- else don't show when just 1 of /sandbox or /testcases exists -->}} </div>{{#ifexist:{{{1|{{SUBJECTPAGENAME}}/doc}}}|{{{{{1|{{SUBJECTPAGENAME}}/doc}}}}}}} <div style="clear:both;" /></div></div>