WordPress – Put a variable in php _e

I’m using wordpress for one of my websites and the theme that I’m using has a metro-styled tiles slider.

Upon hover on a tile, I see this string “more”. I checked the slider config for this type of slider and found that php _e is being used to get this string.

<div class="box box-1">
                        <a href="<?php echo $slide['slide_url']?>" ><img src="<?php echo $slide['slide_src']?>" width="306" height="391" alt="" /><span><?php _e('more','tfac');?></span>

Is it possible to change this to a variable through php echo or something? I have configured the slider settings to accept a custom value through the variable $slide_title.

array('name' => 'Slide Title',
                        'desc' => 'Change hover text here',
                        'id' => 'slide_title',
                        'value' => '',
                        'type' => 'text',
                        'divider' => true),

But despite replacing the php _e line with php echo $slide_title, I still see ‘More’ on hover.

I checked the theme’s PO file and found this –

 #: E:wamp1wampwwwmvibes.mdwp-contentthemesmvibes-parent/theme_config/extensions/slider/designs/gallery/template.php:8
 #: E:wamp1wampwwwmvibes.mdwp-contentthemesmvibes-parent/theme_config/extensions/slider/designs/gallery/template.php:12
 msgid "more"
 msgstr ""

What do I do?