amgento 2 addcustom link to toplinks
<referenceBlock name="header.links">
<block class="Magento\Framework\View\Element\Html\Link" name="custom-header-link">
<arguments>
<argument name="label" xsi:type="string" translate="true">Custom Header Link</argument>
<argument name="path" xsi:type="string">*/*/*</argument>
</arguments>
</block>
</referenceBlock>
<referenceBlock name="top.links">
<block class="Magento\Framework\View\Element\Html\Link" name="custom-top-link">
<arguments>
<argument name="label" xsi:type="string" translate="true">Custom Top Link</argument>
<argument name="path" xsi:type="string">*/*/*</argument>
</arguments>
</block>
</referenceBlock>